Various systems using a pair of detectors to determine the spatial position of a leak in a piping system have been proposed. For example, according to Coulter et al., U.S. Pat. No. 4,858,462, a pair of spaced-apart detectors may be attached to a piping system. The phase difference between the signals is correlated to correspond to the difference in travel time of the acoustic signals to each of the detectors. By measuring this offset, the relative position of the acoustical emission, and thus the relative position of the leak, is determined. A threshold detection level is set to remove background noise. Coulter et al. note that multiple detectors could be utilized to determine a three-dimensional position within a volume.
Nordstrom et al., U.S. Pat. No. 5,058,419, provides another example of an acoustic pipe leak detection system having remote sensors, wherein the time lag between the output of each of the sensors is calculated at a plurality of frequencies. The time delay value which occurs most frequently from these calculations is utilized to calculate the sound source position.
These and other prior art autocorrelative approaches are inadequate because they fail to teach a detection system capable of both identifying and spatially locating signals in the presence of overwhelming levels of background noise.